A hinge structure typically includes two hinge members which are rotatably secured together by a pin or the like. Automatically operated doors, such as those used at shopping centers, schools, or the like are continually operated and are substantially heavier and larger than those used in most homes. As will be understood, continual use of the door submits the hinge structure to extensive wear. Notwithstanding their continual use and the substantial load placed thereon, a hinge structure is expected to perform error-free and with minimum maintenance.
Increases in height and/or weight of the door or the like carried by the hinge members, adds to the frictional sliding contact between the hinge members and thereby increases the wear on the hinge structure. As may be appreciated, and despite the wear on such hinge structures, the hinge members are not normally permitted to longitudinally move relative to each other during operation.
My U.S. Pat. No. 3,092,870, dated June 11, 1963, discloses a pinless hinge structure offering increased performance and durability. Such a hinge structure includes two longitudinally extending hinge members which are rotatably joined along adjacent longitudinal edges by mutually intermeshing gear segments forming part of the hinge members. A clamp member maintains the gear segments in mesh relative to each other while permitting smooth and uniform movement of the hinge members through a full arc of travel of the hinge.
The design and performance of the hinge structure disclosed in the above-identified patent was further enhanced through the provision of a longitudinal thrust bearing which was the subject of my U.S. Pat. No. 3,402,422, dated Sept. 24, 1968. My patented longitudinal thrust bearing comprises an essentially solid bearing member disposed in longitudinally coextensive recesses formed in adjacent longitudinal edges of each rotatable hinge member. The longitudinal dimensions of the bearing member and the recesses in which the bearing member is disposed are such that upper and lower surfaces of the recesses slidably contact upper and lower bearing surfaces of the bearing member disposed therein whereby inhibiting longitudinal movement of one hinge member with respect to the other hinge member.
Several thrust bearings are typically arranged along the length of the hinge structure. Providing several thrust bearings along the length of the door, however, increases both labor and material costs involved in assembling and fabricating the hinge structure. As will be appreciated, each additional thrust bearing member increases the material costs involved in fabricating the hinge structure.
Since the thrust bearings used in a pinless hinge structure are not subject to direct compression loading, as in the case of conventional hinges having interlocking knuckles, the longitudinal length of each lateral recess and corresponding length of each thrust bearing is partially determined by the cantilevered loading applied to each thrust bearing. It has been found that insufficient length of the thrust bearing will result in twisting of the thrust bearing as it transfers the load across the adjacent lateral recesses in the opposing hinge members. To maximize the load bearing capability of a thrust bearing for a pinless hinge structure, it is desirable that the ratio of the longitudinal dimension of the thrust bearing is increased relative to the width of the thrust bearing. Increasing the longitudinal dimension of the thrust bearing, however, involves removal of additional material from the hinge members which adversely affects the lateral strength of the hinge structure.
Because of the continual relative sliding engagement between the hinge members and bearing surfaces, such thrust bearings do, on occasion, require replacement. Replacement of any or all of the thrust bearings normally requires complete disassembly of the hinge structure from the associated door. As will be appreciated, repairs in a door leading to a commonly-frequented building such as a school, hospital, or the like interrupts or limits accessibility to such a building.
Even if only for a short time period, such interruptions to building access are undesirable and, therefore, should be maintained to a minimum, if not eliminated. As will be appreciated, the ability to extend wearability of the hinge structure will reduce maintenance costs, repairs, and thereby improve hinge performance.